amdx wrote:
"Richard Clark" wrote in message
...
On Fri, 19 Mar 2010 17:42:15 -0500, "amdx" wrote:

Richard, after I read your letter I did a little better checking and
found
my signal is not weak it is to strong, I'm getting interference from other
frequencies.
Also I get stations on the wrong frequency.
I went out and collapsed the antenna to minimum about 1/3 of what it was
and
my problem station is perfect and the other station I listen to is still
good. The local
NPR station isn't good though. But I can download the podcast of Science
Friday :-)
Thanks, Mike
Hi Mike,

Normally, a too strong signal is not a problem with FM as FM literally
locks onto the strongest signal and rejects the competitors. This is
not a characteristic of the RF wave, but rather the modulation
employed.

Collapsing your antenna is the same thing as moving it.

Now, as to your experience of receiving signals on the wrong
frequency, that is a classic situation of image rejection being poor
due to the lack of a tuned front-end (something that dissappeared with
the dinosaurs). If I were to guess on the basis of 40 year old
experience fixing these suckers, your off-frequency signals are
probably shifted by twice the IF frequency of your receiver. The
classical FM IF frequency of 10.7 MHz might apply, but time has
marched on and designers may select their own. This old standard
would argue that you shouldn't experience images except where they
would be out-of-band (the 88-107 band with this IF would force that).
A simple test is to tune into at least two of these off-frequency
stations, note what frequency they should be and subtract the
frequency where they appear. If you are having image issues (no, this
is not a self-help hint), the two or more stations should come up with
the same differences.

If you come up with the same number, AND you have trouble with
interference from adjacent stations (there are guard bands to prevent
this), THEN you have one crappy receiver.

73's
Richard Clark, KB7QHC

The receiver is an undercounter mounting Sony AM/FM, radio with CD.
Nothing great, but Sony ususally does a fair job.
Mike


I have learned not to trust any radio that's newer than 30 years,
whether name-brand or not. And that's from experience. Unless it is from
companies like Icom.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.